From: Sergey Dyasli <sergey.dyasli@citrix.com>
Date: Mon, 5 Nov 2018 14:02:22 +0000 (+0100)
Subject: x86/boot: enable NMIs after traps init
X-Git-Tag: archive/raspbian/4.11.1-1+rpi1^2~53^2~18
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=e2436396ed340ade278c29faa9da52a0bd4ae7bc;p=xen.git

x86/boot: enable NMIs after traps init

In certain scenarios, NMIs might be disabled during Xen boot process.
Such situation will cause alternative_instructions() to:

    panic("Timed out waiting for alternatives self-NMI to hit\n");

This bug was originally seen when using Tboot to boot Xen 4.11

To prevent this from happening, enable NMIs during cpu_init() and
during __start_xen() for BSP.

Signed-off-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
master commit: 072e054359a4d4a4f6c3fa09585667472c4f0f1d
master date: 2018-10-23 12:33:54 +0100
---

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index fdb022875a..72e65b6e1a 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -831,6 +831,9 @@ void cpu_init(void)
 #define CD(register) asm volatile ( "mov %0,%%db" #register : : "r"(0UL) );
 	CD(0); CD(1); CD(2); CD(3); /* no db4 and db5 */; CD(6); CD(7);
 #undef CD
+
+	/* Enable NMIs.  Our loader (e.g. Tboot) may have left them disabled. */
+	enable_nmis();
 }
 
 void cpu_uninit(unsigned int cpu)
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 2860c425ef..ecb0149849 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -702,6 +702,9 @@ void __init noreturn __start_xen(unsigned long mbi_p)
 
     /* Full exception support from here on in. */
 
+    /* Enable NMIs.  Our loader (e.g. Tboot) may have left them disabled. */
+    enable_nmis();
+
     if ( pvh_boot )
     {
         ASSERT(mbi_p == 0);